The fly you see buzzing around inside may represent far more of a problem than it appears on the surface. While most solitary flies you find indoors are outdoor invaders and don’t pose more than a risk of contamination and annoyance to those in the vicinity, two more grim possibilities exist. The first is that the fly in question is about to, or just did, lay dozens to hundreds of eggs somewhere inside your facility. The second undesirable situation is that the fly you just saw zoom past you emerged from somewhere inside your business.